This work is part of the European project DACCIWA WP2 “Air pollution and Health”. This study aims to characterize urban air pollution levels through the measurement of NO2, SO2, NH3, HNO3 and O3 in Abidjan and Cotonou, two major cities in West Africa. Measurement of inorganic gaseous pollutants i.e. NO2, SO2, NH3, HNO3, O3 were performed during a mid-termcampaign from December 2014 to April 2017, using INDAAF passive sampler at different sites representative of major sources of air pollution in West Africa (domestic fires, traffic and waste burning) from December 2014 to April 2017. During this study period, 2 intensives campaigns were conducted during dry seasons (15 December 2015-15 February 2016 and 15 December 2016- 15 February 2017). Air quality networks consisting of 27 measurement sites in Abidjan and 8 in Cotonou have been installed. In addition to the sources of air pollution already mentioned, these intensive measurement campaigns took into account other sources such as industrial, residential and suburban areas. All the validated results obtained made it possible to create an original database. To date, it is the longest (28 months) and most comprehensive database on concentrations of gaseous pollutants in urban environments in West Africa. This database was initially used to assess the contribution of each of the main sources of pollution to pollutant concentrations at each of the mid-term measurement sites. Then, temporal variations gaseous pollutant concentrations were studied, thus making it possible to define the average levels of pollutants in Abidjan and Cotonou. The results indicate low seasonality of pollutant concentrations although somewhat higher concentrations are generally measured during the dry season from November to February. At all the measurement sites, NH3 and NO2 are the major pollutants with higher concentrations at the domestic fire sites of Abidjan and Cotonou traffic respectively. The study of the spatial distri